The accumulation of ice on various surfaces of an aircraft can produce disastrous results. Accordingly it is important for a pilot to know when ice starts to appear and to take measures to avoid serious consequences. For example, the pilot may turn on surface heaters, make changes in speed or elevation, changes in the angle of attack and/or seek the nearest airport before the problem becomes critical. Further, it is important for a pilot to know when accumulated ice in a dangerous amount has formed on the surface of the aircraft.
Ice detectors are known. For example, a patent of Gaertner, U.S. Pat. No. 3,571,709 discloses a detector for measuring icing rates over a plurality of periods of time. As disclosed therein, an icing rate detector utilizes an icing switch and a heater, which are mounted on the outside of an aircraft. When ice forms on the switch, it closes and energizes a heater, which then melts the ice and causes the switch to open. The heater thus is cycled on and off when the aircraft is subjected to icing conditions. A rate detector circuit measures the rate at which power is consumed over a fifteen second period and over a two-minute period. These rates are directly proportional to the rate at which ice is formed on the aircraft.
A more recent patent of Mayer, U.S. Pat. No. 4,755,062 discloses a process and measuring probe for the determination of ice or snow formation. As disclosed therein, the heat abstraction intensely occurring due to ice or snow is measured and used as a signal for ice or snow formation. A current meter for determining increased power consumption determines the intensified heat abstraction on the cold conductor. The intensified heat abstraction on the cold conductor is determined by a current meter for determining increased power consumption or by a thermister which is an heat conducted connection with a cold conductor and switches the power supply of the cold conductor on and off as a function of the temperature.
Notwithstanding the above, it is presently believed that there may be a large commercial market for an improved ice detector in accordance with the present invention. A commercial market should develop because the improved system and element in accordance with the present invention warn a pilot of hazardous icing conditions; enable a pilot to determine the thickness of the ice as well as the condition when icing may be at a relatively high rate. In addition, ice detectors in accordance with the present invention indicate the total ice accumulated on the aircraft. It is also presently believed that such systems can be manufactured and sold at a competitive cost, can be readily installed on new aircraft as well a retrofitted on existing aircraft, are compact, durable, accurate and readily serviced. Further advantages will become evident from the following specification.